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The seismic data written to tape in the dog house, whether on land or at sea, are not ideal for interpretation. To create an accurate picture of the subsurface, we must remove or at least minimize artifacts in these records related to the surface upon which the survey was performed, artifacts related to the instrumentation and procedure used, and noise in the data obscuring the subsurface image. Treatment of the data to achieve these ends is commonly referred to as ''seismic data processing''. Through processing, the huge volumes of data taken in the field are reduced to simple images for display on paper or the work station screen. This simple image, while it contains less data about the subsurface, is readily accessible to the interpreter and has many of the artifacts and errors just listed removed. [[:file:basic-seismic-processing_fig1.png|Figure 1]] shows a single, unprocessed (raw) field record taken from a line. [[:file:basic-seismic-processing_fig2.png|Figure 2]] is the same line of data after processing to illustrate how the field records are turned into an interpretable image.

The [[seismic data]] written to tape in the dog house, whether on land or at sea, are not ideal for interpretation. To create an accurate picture of the subsurface, we must remove or at least minimize artifacts in these records related to the surface upon which the survey was performed, artifacts related to the instrumentation and procedure used, and noise in the data obscuring the subsurface image. Treatment of the data to achieve these ends is commonly referred to as ''seismic data processing''. Through processing, the huge volumes of data taken in the field are reduced to simple images for display on paper or the work station screen. This simple image, while it contains less data about the subsurface, is readily accessible to the interpreter and has many of the artifacts and errors just listed removed. [[:file:basic-seismic-processing_fig1.png|Figure 1]] shows a single, unprocessed (raw) field record taken from a line. [[:file:basic-seismic-processing_fig2.png|Figure 2]] is the same line of data after processing to illustrate how the field records are turned into an interpretable image.

[[file:basic-seismic-processing_fig1.png|thumb|300px|{{figure number|1}}A single shot record as it is recorded in the field. The shot is at station 60. There were 120 geophones laid out in this “split” spread. Two seconds of data were recorded. © Landmark/ITA.]]

[[file:basic-seismic-processing_fig1.png|thumb|300px|{{figure number|1}}A single shot record as it is recorded in the field. The shot is at station 60. There were 120 geophones laid out in this “split” spread. Two seconds of data were recorded. © Landmark/ITA.]]

==Typical processing steps==

==Typical processing steps==

<gallery mode=packed>

<gallery widths=200px heights=200px mode=packed>

file:basic-seismic-processing_fig3.png|{{figure number|3}}The shot record of Figure 1 after the application of a gain recovery algorithm to replace the energy lost as the signal traverses the earth. © Landmark/ITA.

file:basic-seismic-processing_fig3.png|{{figure number|3}}The shot record of Figure 1 after the application of a gain recovery algorithm to replace the energy lost as the signal traverses the earth. © Landmark/ITA.

file:basic-seismic-processing_fig4.png|{{figure number|4}}The shot record after a statistical deconvolution process has been applied to “shorten” the wavelet and increase time resolution. Copyright Landmark/ITA.

file:basic-seismic-processing_fig4.png|{{figure number|4}}The shot record after a statistical deconvolution process has been applied to “shorten” the wavelet and increase time resolution. Copyright Landmark/ITA.

===Dip moveout (DMO) correction===

===Dip moveout (DMO) correction===

NMO corrections are made under the assumption of horizontal planar reflectors. If the reflector has appreciable dip, then the actual movement will be slightly different. The DMO correction is a method for estimating the effect of dip on moveout and removing it from the records as well.

NMO corrections are made under the assumption of horizontal planar reflectors. If the reflector has appreciable [[dip]], then the actual movement will be slightly different. The DMO correction is a method for estimating the effect of dip on moveout and removing it from the records as well.

===Common midpoint (CMP) stack===

===Common midpoint (CMP) stack===

This is the single most effective step for noise reduction in the processing flow. The shooting procedure results in many traces being acquired with the point midway between [[source]] and [[receiver]] (called the midpoint) being coincident on the earths surface. The only difference between the traces is the distance between source and receiver (offset). Once these traces have been NMO (and DMO) corrected, they are really redundant samples of the same reflection. Adding them together increases the signal to random noise ratio by the square root of the number of redundant samples. The process reduces the field data to a stacked section consisting of one trace for each midpoint location, assumed to have been recorded with a shot and receiver coincident at the midpoint location (see [[:file:basic-seismic-processing_fig2.png|Figure 2]]).

This is the single most effective step for noise reduction in the processing flow. The shooting procedure results in many traces being acquired with the point midway between [[source]] and [[receiver]] (called the midpoint) being coincident on the earths surface. The only difference between the traces is the distance between source and receiver ([[offset]]). Once these traces have been NMO (and DMO) corrected, they are really redundant samples of the same reflection. Adding them together increases the signal to random noise ratio by the square root of the number of redundant samples. The process reduces the field data to a stacked section consisting of one trace for each midpoint location, assumed to have been recorded with a shot and receiver coincident at the midpoint location (see [[:file:basic-seismic-processing_fig2.png|Figure 2]]).

===Poststack filter===

===Poststack filter===

[[Category:Geophysical methods]]

[[Category:Geophysical methods]]